Roof bolt with a flexible tension member and cup-shaped expansible securing means



1963 .0. .HARDING ETAL 3,

ROOF BOLT WIT FLEXIBLE TEN N MEMBER AND CUP-SHAPED EXPANSIBLE SEC NGMEANS Filed May 28, 1959 2 Sheets-Sheet l II.- zlllilllllliui ill:

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' ROOF BOLT WITH A FLEXIBLE TENSION MEMBER AND CUP-SHAPED EXPANSIBLESECURING MEANS Filed May 28. 1959 2 Sheets-Sheet 2 ig /a ,gZ7 W/ 2335/ 61 6" M- 3 077 809 ROOF BOLT WITH A FLEXlBLE TENSION MEM- BER ANDCUP-SHAPED EXPANSIBLE SECUR- ING lVIEANS Denys Frederick Harding,.Falmouth, Cornwall, Robert Edward Campbell, Doncaster, and John Baker,liessa- 'carr, Doncaster, England, assignors to British Ropes Limited,Doncaster, England, a British company Filed May 28, 1959, Ser. No.316,476

:Claims priority, application Great Britain May 28, 1958 Claim. ca. 852.4)

.or near the blind end) and at the other end, there is attached a screwcompression means, arranged to bear onto the rock or other surfacearound the mouth of the hole and to apply pressure to this and,preferably, the surrounding area. Such tie bolts have many practicalapplications. They are, for example, commonly used in mines (bothmetalliferous and carboniferous) as root supports, and will hereinafterbe referred to as roof bolts, without intending thereby any limitationof the invention to the supporting of roofs. Roof supports are required,for example, when mining operations are being conducted in rock stratawhich have become badly faulted and broken up, and the bolts areemployed to hold or secure the broken strata to the overlying solid rockwhilst working and removal of rock, or ore, proceeds. To this end blindholes (usually several feet deep) are drilled to a prescribed patternthrough the broken strata into the solid rock; the roof bolts are theninserted into the holes and the securing means in the blind holeactuated, usually by rotation of the roof bolt, to cause it to expandinto holding engagement with the solid rock. The screw compression meansis then tightened up against the face of the broken strata, preferablywith the aid of a pneumatic torque wrench, to a prescribed ft./lbs.torque load (the amount of which is determined by the type of groundbeing worked), whereby the bolt acts, under tension, to secure thebroken strata to the solid rock.

In roof bolts as at present constructed, the tie member is of rigidconstruction which, in some circumstances, makes insertion and removalof the bolts a time consuming, if not impracticable, operation,especially in confined spaces (i.e. low headings) and/or in cases, ascan frequently occur, where drills have wandered and the hole is notstraight.

It is an object of this invention to avoid or reduce these difficulties.

The invention provides a roof-bolt comprising an elongated tensionmember comprised of a length of flexible steel wire, cable or rope toeach end of which is secured a screw threaded end piece, an expansionshield or other expansible securing device attached to one of the endpieces for engagement in the hole and on the other end piece a nut and abearing plate for engagement under pressure from the nut with thesurface to be supported.

Preferably the cable or rope is capable of transmitting a substantialtorque load in each direction, without unlaying. Thus the rope maycomprise rope strands laid 1 United States Patent various ways ofwhich-several examples also are given later.

Some specific embodiments of roof bolts according to .the invention willnow bedescribed, by way of example,

and with reference to the accompanying drawings, in which:

FIGURE 1 shows a complete roof bolt, FIGURE '2 shows one of theend-pieces in position on 'the rope ready for swaging,

FIGURE 3 shows, in section, the end piece and-rope of FIGURE 2 afterswaging,

FIGURE 4 is a section showing an alternative form of :end piece on theend of a rope,

FIGURE 5 is a section through a strandrope used in the bolt,

FIGURE 5A is a quite diagrammatic view in section of :a completed ropeused in forming the bolt, the windings of the individual strands notbeing indicated since these are clearly shown in FIGURE 5,

FIGURE 6 is a side view showing one construction of expansion shield,

FIGURE 7 is a view similar to FIGURE '6 but illustrating the operationof inserting the shield into a hole,

FIGURE 8 is an elevation of one of the expansible cups used in theshield shown in FIGURES'6 and 7,

FIGURE 9 is a plan view of the cup shown in FIG- URE 8,

FIGURE 10 is an elevation of another form of expansiblecup, and

FIGURE 11 is a view, corresponding to FIGURE 6, showing anotherconstruction of expansion shield.

In .the construction shown in FIGURE 1 the tension member is composed ofa length of wire rope 20 to each end of which is secured a screwthreaded end piece 21, v 22 co-axial with the end of the rope. The endpiece 21 'has threaded over it a gripping device, commonly known as anexpansion shield, which comprises a short externally andcircumferentia'lly serrated tube-like member 23 with, in this example,four equi-spaced longitudinal slits 24 extending from one end ahnost tothe other end, thereby forming four resilient leaves 25. This tube ismade from malelable iron in the form of a casting. In addition to theserrations, each leaf has an axial or longitudinal rib 26 near its freeend to provide an anti-rotation key. Fitting within the first-mentionedend of the tube there is a cast, internally-threaded, conical nut 28which is screwed onto the starting end of the thread of the end piece 21and is arranged, on rotation of the end piece into the nut, to enterbetween and expand the leaves 25. A shoulder 29 on the end piece limitsthe movement of the tube 23 along the end piece.

The end piece 22passes through a hole in a steel bearing plate 39,which, in this example, is square or rectangular. There is also a nut 31screwed onto the end piece.

In use, when it is required to insert the roof'bolt, the conical nut 28is screwed back to permit the leaves 25 toclose in and contract to theirminimum diameter.

This end of the bolt is then inserted into a prepared hole in the rockor other material it is required to support, until almost the wholelength of the bolt is within the hole.

The end piece 22, of which the screwed portion remains projecting fromthe hole, is rotated until sufi'lcient torque has been transmitted(usually around ft./lbs.) to draw the conical nut into the tubularmember 23 and thereby to separate the leaves 25 into gripping engagementwith the walls of the hole.

, The bearing plate 30 is then slid over the threaded portion of the end,piece 22, followed by the -nut 31; ;a pneumatic torque wrench is thenset to the desired load 3 and applied to the nut. The plate 30 isthereby brought into pressure engagement with the roof, or other surfaceit is desired to support, and the cable acts as a tension member whichsupports the lower or outer structure.

In those cases where it is practicable and desirable to be able torecover the bolts when the workings are abandoned, the aforesaid roofbolt is removed by loosening the nut 31 on the bearer plate, anddelivering an upward or endwise blow to the exposed end of the bolt.This drives the conical nut upwards or inwardly of the hole and releasesthe expansion shield. If necessary or desirable the tension member maybe rotated a few turns anticlockwise before the upward blow isdelivered, in order to ensure that the shoulder 29 is withdrawn from theend of the shield.

As already stated, various methods of forming and affixing the screwedend pieces to the rope or cable may be adopted. In one method,illustrated in FIGURES 2 and 3, the end piece to be attached has, at oneend, an externally threaded portion 34 and at the other end an internalsocket 35 coaxial with the threaded portion. Externally the socketportion has two diameters. The end of the rope 20 is inserted into thesocket 35 and the portion 36 of larger diameter is swaged or presseddown to at least the size of the smaller portion 37. This plasticallydeforms the metal of the socket wall into gripping relation with therope and also tends to cause the free ends of the component wires of therope to splay outwardly into the inner, unswaged end 38 of the socket(see FIGURE 3) and to provide an additional key or anchor.

Another method, illustrated in FIGURE 4, is to produce the end piecefrom a length of tube 40, into which the end of the cable, or rope 20,is inserted. The tube is then swaged, over its entire length, onto thecable, or rope, and finally a thread 41 is cut or rolled along the endportion of the tube.

A third method is to insert the end of the cable, or rope, into a tubefor about two thirds the length thereof, and swage the tube from the endat which the rope or cable has been inserted, almost to the end of therope, thereby gripping the rope whilst leaving the ends of the wiresfree to splay out as already described. A length of screwed rod is theninserted into the other end of the tube, leaving a portion projectingtherefrom. Finally, the tube is swaged onto the rod, the swaging beingcontinued until the tube has been deformed firmly into the thread, andthe thread itself has been deformed into interlocking engagement withthe tube.

The rope used in the above examples, and in those later described, has across section such as diagrammatically suggested in FIGURE A, comprisingsix outer strands 42 laid over a core strand 43. The outer strands 42and the core strand 43 are preferably of 9 x 9 x 1 construction, assuggested in FIGURE 5, each consisting of a suitable core 44 wound withan intermediate layer of windings 45 and an outer layer of windings 46.The outer strands 42 are wound around the core strand 43 the oppositehand to the winding of the individual elements of the core strand 43.The rope is capable is transmitting substantial torque in each directionof rotation and has substantial tensile strength. Furthermore it has agreater resistance to shear than a solid rod, shearing forces sometimesbeing applied to roof bolts due to rock strata tending to slide on oneanother.

FIGURES 6-9 show another construction of expansible securing device. Inthis construction the device comprises a succession of four cup-shapedmembers 50 strung or threaded loosely over the screw-threaded portion ofthe end piece 21 against the shoulder 29. Each of the cup shaped members50 has a base 51 with a hole 52 threaded over the end piece and sideswhich are divided by notches 53 into tongues 54. The tongues 54 areflexible, or flexibly connected to the base, face along the length ofthe rope 20 and diverge or tend to diverge, outwardly from the base sothat, as seen in FIGURE 7, the tension member may be pushed into a hole56 with the bases 51 leading and the tongues 54 compressed against thewalls of the hole but withdrawal of the member from the hole is resistedby the tongues 54 engaging the walls of the hole with a toggle actionand tending to open outwardly and to dig into the walls. In thisconstruction the expansion is effected by the pull of the cable, withoutrotation. The cups are held on the end-piece by a nut 57 and separatedby collars or distance pieces 58. The cups are made of a high impactelastomer such as that mentioned later.

The prongs of the several cups in the succession are staggered and theymay be of varying lengths. The depth of the notches 53 may also bevaried.

In a modification of the above construction, the plastic cups are, asshown in FIGURE 10, shallow and without prongs or tongues. The surfaceof the cups, or the1r outer edges may in either construction, becorrugated. Again the peripheral edges or the edge of the tongues may betoothed or serrated.

In the construction shown in FIGURE 11 the four cup-shaped members ofthe example shown in FIGURE 6 are reversed on the end piece so thattheir mouths face towards the adjacent end of the member. The tongues54a or walls of the cups are resiliently biased inwardly. Within eachcup there is a tapered (frusto-conical) member 60 adapted by movementinto the cup to open out the mouth of the cup (i.e. to spread thetongues). The larger end of each of the intermediate tapered memberssupports the base of the adjacent cup. The last such member (i.e. theone 60a nearest the end of the bolt) is screwed onto the end piece 21 orthere is a nut on the bolt which bears on this member. The cups may bewith or without tongues, as described above. In the application of thisexample, the tapered members are withdrawn to permit the walls of thecups to contract inwardly. The bolt is thrust into the hole with themouths of the cups leading. Rotation of the tension member will thenscrew it into the nut or last tapered member, which has the effect ofexpanding the cups into gripping engagement with the walls of the hole.

A suitable elastomer for the manufacture of the cups is that sold by theBritish Geon Co. Ltd. under the name R.A. High Impact polyvinyl chloridebut other elastomeric substances having similar physical and chemicalcharacteristics may be used.

It is within the invention to replace the succession of cups in each ofthe constructions described by only a single cup.

The bolts according to the invention may be used for supporting roofs inmines from overlying strata or they may similarly be used for securingmine faces and floors.

We claim:

A roof bolt adapted for anchoring insertion into a blind drill hole in amine roof or the like, said bolt comprising an elongated tension membercomprising a length of flexible multi-strand steel rope, comprising acore strand the outer windings of which are laid in one hand and ropestrands laid over said core strand in the hand opposite to the laying ofsaid outer core windings, an end piece at each end of said length ofrope each comprising an externally screw-threaded rod portion and asocket portion coaxial therewith, said socket portion receiving andgripping an end of said rope, a radially expansible securing devicecarried by one of said end pieces and adapted to be inserted first intosaid hole in installing the bolt and ultimately to be expanded intoanchoring contact with the walls of said hole; said expansible securingdevice comprising a plurality of cup-shaped elements, each comprising abase portion and flaring side portions adapted when the bolt isinstalled to engage the walls of the hole, said cup-shaped elementsbeing loosely threaded upon the end piece at one end of the bolt andopening toward the adjaient end of said end piece, and a plurality oftapered members loosely threaded onto said end niece one disposedbetween each of said cup-shaped elements and with its smaller endentering the mouth of that cup of the adjacent pair which is furtherfrom the end of the bolt, and serving to press upon and expand saidcupshaped element upon the occurrence of endwise pressure on thecup-shaped elements and connecting members, and a tapered terminalmember screw-threaded onto the end piece, having its smaller endentering the end cup-shaped element and said terminal member adapted tomove inwardly upon rotation of said bolt to expand its contactingcup-shaped element and to transmit wedging pressure along the successionof alternating cup-shaped elements and tapered intervening members; abearing plate of greater radial compass than the securing device or thehole itself and having a centrally disposed opening slidably receivingthe other of said end pieces and a nut screwed onto said last named endpiece over said plate and adapted to be brought to bear thereupon tolock the bolt and its named associated parts in place.

References Cited in the file of this patent UNITED STATES PATENTS 36,014Meissner July 29, 1862 179,237 Ward June 27, 1876 861,573 Budd July 30,1907 1,031,462 Paine July 2, 1912 1,278,025 Salmons Sept. 3, 19181,434,394 Matthes Nov. 7, 1922 1,643,110 Briggs Sept. 20, 1927 2,129,439Noble Sept. 6, 1938 2,970,444 Peter Feb. 7, 1961 FOREIGN PATENTS1,005,474 Germany Apr. 4, 1957

